Automated blood analysis system

ABSTRACT

A system for automatically withdrawing blood from a patient and testing various parameters of the blood, such as oxygen saturation, hemoglobin, gas content (PO2, PCO2) and pH, includes a withdrawal unit which automatically withdraws a measured volume of blood, and returns all of it to the patient except a small measured quantity which is provided to an analysis unit that measures the gas content and pH. The withdrawal unit includes provision for continuously monitoring patients&#39;&#39; blood pressure, irrigation from a standard I. V. source between blood withdrawals, or a constant low flush of saline, alternatively, as well as detection of any air in the blood, which results in shutting down the system and activating an air alarm. The withdrawal unit also has provision for automatically withdrawing a small sample of blood, measuring oxygen content, and returning all blood to the patient, all on a programmed basis. The analysis unit includes two-point gas and pH calibration and includes use of calibration fluid for washout. In each complete use cycle, blood from the withdrawal unit is washed into the analysis unit and blood in the analysis unit is moved and washed out using saline, water and calibration fluids. The withdrawal unit may be used alone to acquire blood samples, and the analysis unit may be fed by more than one withdrawal unit or by manually-acquired blood specimens.

United States Patent Clark et al.

Oct. 1, 1974 AUTOMATED BLOOD ANALYSIS SYSTEM [75] Inventors: Justin S.Clark; Lloyd George Veasy, Salt Lake City, Utah [73] Assignee: PrimaryChildrens Hospital, Salt Lake City, Utah [22] Filed: Dec. 29, 1972 [21]Appl. No.: 319,561

[52] US. Cl. 128/2 G, 128/214 B, 128/214 E,

[51] Int. Cl. A6lm 5/00, A6lb 5/00 [58] Field of Search 128/2 L, 2 G, 2R, 214 B, 128/214 E, 214 F; 356/39-42 [56] References Cited UNITEDSTATES PATENTS 2,455,810 12/1948 Ryan 128/2 G 2,700,320 l/l955 Malmros128/2 L 3,029,682 4/1962 Wood 128/2 L X 3,043,303 7/1962 Still 128/214 E3,489,145 l/l970 Judson et al... 128/2 R 3,648,694 3/1972 Mogos et all28/2l4 F Primary ExaminerAldrich F. Medbery Attorney, Agent, orFirm-Mr. Lynn G. Foster [57] ABSTRACT A system for automaticallywithdrawing blood from a patient and testing various parameters of theblood, such as oxygen saturation, hemoglobin, gas content (P PCO and pH,includes a withdrawal unit which automatically withdraws a measuredvolume of blood, and returns all of it to the patient except a smallmeasured quantity which is provided to an analysis unit that measuresthe gas content and pH. The withdrawal unit includes provision forcontinuously monitoring patients blood pressure, irrigation from astandard I. V. source between blood withdrawals, or a constant low flushof saline, alternatively, as well as detection of any air in the blood,which results in shutting down the system and activating an air alarm.The withdrawal unit also has provision for automatically withdrawing asmall sample of blood, measuring oxygen content, and returning all bloodto the patient, all on a programmed basis. The analysis unit includestwo-point gas and pH calibration and includes use of calibration fluidfor washout. In each complete use cycle, blood from the withdrawal unitis washed into the analysis unit and blood in the analysis unit is movedand washed out using saline, water and calibration fluids. Thewithdrawal unit may be used alone to acquire blood samples, and theanalysis unit may be fed by more than one withdrawal unit or bymanuallyacquired blood specimens.

12 Claims, 6 Drawing Figures 4o 381O -E! LV. spsl OXIMETER SOURCE 1184ap p SALINE 1H0 WASTE ifl ez uz loa SALINE 7z lOZ ([70 \/7e UUJIWI- I681 66 I03 198 J PRESSURE 78 TRANSDUCER :94 I68 I34? ;|ss I38 p A) lCONSTANT 8 2 76'2, 2 VOLUME 80b -n4 2m 4 PUMP RES R ll8 ll6 r Q [32 I80?f I28 :42 144 1 80d I82 we 1 :28

. I56 M6 I 122 |54 T0 BLOOD CUP [50f 3 0 J (was) Am 22 PAIENI'EBIJBI umSIIEEI 10F 5 4|2 sAIvIPI E GAS 4|O FZOSAMPLE pH XFIG. 4

WITHDRAWAL UNIT (FIG.2)

ANALYSIS UNIT (FIG. 3

36? E4, 387 O I L OXIMETER PRESSURE TRANSDUCER lIoo SOA/

SOURCE 8: PUMP CALCULATION UNIT (NOT SHOWN) WASTE INDICATORS iOXIME-TE Rzea kms ELEC. 242 EI REF.

1] pH ELEC.

FIGS

FIGQI (SYSTEM) 8 PSI SALINE -IIo SALINE JIGS I38 CONSTANT VOLUME 3 PUMPRESERVOIR (W FIG..2 (WITHDRAWAL UNIT) TO BLOOD CUP (FIG. 3)

PSI AIR }FIG. 2 I

PMENTED 3.838.562

i 9 f SEE! 30F 5 MAIN 34o POWER ox 7 POWER 38 SOURCE SOURCE ON/OFF 342VALVE ONE L.E.D POWER gga i, POWER I TO SOURCE TIMER SOURCE FIG.

346 Q r TEST 39% AIR DETECTOR352 350' I56 348 WITHDRAWAL PUMP PULL 36 7No US RPM 7 I64 OX-RON 6 @368 MOTOR WITHDRAWAL PUMP VALVE-RESR.

364 L I60 5 o 352 BLOOD CUP VALVE PATIENT -370 A J o o 354 as? SAMPLE pH4|O 4 OX'R. 0 R 05 To OFF 372 359 SAMPLE GAS 3 FIIG.

SIXTEEN 39s 374 TRACK J GAS/pH VALVE- pH I ROTARY TIMER BUFFER'ONE mm21.3 4 HIGH 'CONC. CALIB. GAS '95 CALIB. GAS VALVE -I ow H20 PUMP 5BUFFERTWO PUMP J eAs BLOOD DETECTOR 2; 3 W pH BLOOD DETECTOR AIR ALARMANALYSIS PuMP PULL 4I4 J k J 54 o A.D.'s (FIG.2) o I A 3s4 56 5 430 254?pH BLOOD DET. f 428 426 F' GAS BLOOD DET. o I

FIG. 4 (TIMING UNIT) AUTOMATED BLOOD ANALYSIS SYSTEM The inventiondescribed herein was made in the course of work under a grant or awardfrom the Department of Health, Education, and Welfare.

BACKGROUND 1. Field of Invention This invention relates to automatedblood analysis systems, and more particularly to apparatus forautomatically withdrawing and testing blood.

2. Prior Art The proper management of patients who are critically illwith respiratory or cardiovascular disorders requires frequentmonitoring of various blood parameters such as oxgygen saturation, gascontent and pH. While adequate oxygenation is necessary for maintenanceof life, it is also important to avoid excessively high arterial POparticularly in new born infants, in order to prevent RetrolentalFibropl'asia and possible central nervous system damage. Similarly, theduration of high oxygen concentrations must be kept to a minimum ininfants to prevent possible toxic effects in the lungs. There arenumerous other situations, such as in diagnosis of critical illness,monitoring a patients condition during certain corrective procedures,and in intensive care programs wherein blood parameters must befrequently analyzed.

However, frequent manual withdrawal of blood is undesirable due to theincreased opportunity for the entrance of air emboli in the bloodstream, and to the attendant necessary morbidity, particularly in newborn infants. Similarly, multiple usage of an indwelling catheter hasheretofore nonetheless required rearrangement of external tubing toadjust between blood withdrawal and irrigation configurations, which issubject to human error and which also prevents increased inci dence ofair emboli infusion. Some systems known to the prior art require aconstant flow of blood therethrough which unnecessarily increases bloodcontact with foreign surfaces, which can increase the opportunity forcontamination of the blood, or which may damage the blood. On the otherhand, systems known to the art which discharge withdrawn blood to wasteafter testing thereof have utilized an excessive amount of blood whichbecomes particularly intolerable in the case of critically ill new bornand pre-mature infants. Other systems subject the patient to a risk ofelectric shock due to a continuous contact existing between the patientand electric potentials within the blood testing equipment or sensors.Systems which return blood to the patient cannot be used for destructivetests (such as glucose analysis, flame photometry, etc.).

As is known, it is common to employ saline as a compatible vehicle foruse in blood pumps and tubing systems of blood test units since some ofits chemical properties approach that of blood. However, depending uponthecharacteristics of the individual patient, blood equipment and use,it is possible to infuse undue amounts of saline into the patients bloodstream, threby resulting in a dangerous sodium buildup. Use ofintravenous solutions (I.V.) which are desirable to the patient for itsnutritive or other value, as a vehicle in blood systems avoids thesodium buildup problem, but, on the other hand, has a tendency tocontaminate the system with respect to the blood test transducers whichare used.

LII

Some blood parameters differ markedly from saline and pure water, whichare used for cleaning a system. and may concurrently require a testprinciple which includes a very slow process, such as diffusion across amembrane. Repetitive usage of an effective blood analysis systemrequires automated washout between samples. On the other hand. efficientusage of such a systern, particularly with multiple blood sources.dictates that a rather rapid analysis cycle be achievable. Bloodanalysis units known to the art require both manual cleaning and manualcalibrations between samples.

In addition, systems known to the art do not provide adequate tests formembrane leakage in gas detection tests.

OBJECTS AND BRIEF SUMMARY OF THE INVENTION A principal object of thepresent invention is to provide improved blood analysis capability.

Another object of the invention is to provide in1- proved automaticblood withdrawal and analysis units.

A further object of the invention is provision of a blood withdrawalunit capable of automatic interspersion of blood withdrawal cycles withconstant irrigation or flush cycles for use with a continuouslyindwelling catheter.

Still other objects of the invention include provision of bloodapparatus with improved self cleaning. automatic calibration. shorterequilibration times. and with improved integrity of the test results.

Further objects of the invention include an auto mated blood analysissystem which requires very little blood, isolates hazardous bloodtesting units from the patient, is self-calibrating and self cleaning,and is capable of utilization with multiple automatically or manuallyderived blood specimens.

Other important objects are the provision of an automatic blood testingsystem having: a novel fluid reservoir; capability to returnsubstantially all withdrawn blood to the patient; an analyzer which canbe shifted between and used with any one of several blood withdrawalunits; an analyzer/withdrawal arrangement where only the withdrawal unitrequires sterilization and contamination of the withdrawal unit by theanalyzer is precluded; a combination blood withdrawal/infusion unitwhere intravascular (I.V.) solution flow is continuous, i.e., to thepatient during the infusion mode and to waste during blood withdrawal;initial calibration fluids which are used to displace blood within theblood testing system; a control arrangement based on sensing ablood/transparent fluid interface which moves within the systemaccording to a program.

According to the present invention, an automated blood system adaptedfor connection with an indwelling catheter includes alternativelyoperable means for providing l.V. infusion, constant catheter flush, orblood withdrawal. without necessitating rearrangement of apparatus, bymeans of a novel and improved automated valving arrangement.

In accordance with the present invention, automatic blood analysisapparatus is provided with a plurality of sources of fluid, said fluidhaving a characteristic similar to a characteristic of blood which is tobe tested, said apparatus including testing stations interconnected withsaid fluid sources by valve means programmed in a fashion to providecalibration of said test station prior to the testing of blood therewithand further calibration following the testing of blood therewith. Infurther accord with the present invention, automated blood testingapparatus includes a gas test station and a pH test station, and valvingmeans for applying blood first to said pH test station and then to bothsaid pH test station and said gas test station, the fluid in said teststations being in electrical communication with one another, saidapparatus providing a first test of blood at said pH test station atsaid first time and a second test at said pH station at said secondtime, a substantial variation in the results of said first and secondtests being indicative of a fault at said gas test station. In stillfurther accord with the present invention, washout water used to cleansea test station is provided with a measure of a substance for which bloodis to be tested, thereby to provide the presence of said substance in anamount on the same order of magnitude of the concentration of saidsubstance normally found in a test therefor, whereby to reduce theequilibration time required to perform a test for said substance. Inaccordance still further with the present invention, improvedprogramming and arrangement of valve means enhances the drawing of bloodinto test stations, and the cyclic cleaning of a plurality of teststations with various fluids.

The present invention provides automatic blood withdrawal and/orautomatic blood testing with great safety and at a relatively high rateof speed. Blood/- Transparent fluid interface is minimized by a novelreservoir and the interface serves to control the operation of thesystem. Blood withdrawal apparatus in accordance herewith is capable ofwithdrawing precise amounts of blood, for use in the automated analysisoperations or otherwise, in between the regulated infusion of catheterflushing solution or intravenous irrigation solution. The inventionpermits rapid cyclic testing of different blood specimens, withautomatic washout between tests, and automatic and efficientcalibration. The invention eliminates the need for multiple catheters orreconfigurations of withdrawal systems in order to achieve steady statemonitoring and infusion in conjunction with periodic blood withdrawal.Blood withdrawal may be achieved utilizing solutions which arecompatible with blood testing, or utilizing intravenous irrigationsolutions which avoid a buildup of excessive concentrations ofundesirable compounds in the blood. The automated testing of blood isachieved in accordance with the invention in a manner utilizingextremely small amounts of blood and returning substantially allwithdrawn blood to the patient. Minute amounts of blood used for certaintests are exhausted to waste, thereby avoiding any risk of crosscontamination and blood damage problems. Testing of blood from aplurality of automatic or manually withdrawn specimens in a relativelyshort period of time is readily achieved, clue not only to the completeautonomy of the automated withdrawal and testing units, but as well tofast and efficient washout and calibration procedures. One analysis unitcan Service several withdrawal units. Need for sterilization of theanalyzer is obviated and cross contamination, analyzer-to-withdrawalunit, is avoided. The withdrawal unit may be constructed to both infusel.V. fluid and withdrawal blood, with l.V. fluid being exhausted towaste during the withdrawal mode. Preferably, calibration fluids drivethe blood within the system.

Other objects. features and advantages ofthe present invention willbecome more apparent in light of the following detailed description of apreferred embodiment thereof. as illustrated in the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified block diagramof a system in which the present invention may be incorporated;

FIG. 2 is a schematic block diagram of an automated blood withdrawalunit in accordance with the present invention;

FIG. 3 is a schematic block diagram of an automated blood analysis unitin accordance with the present invention;

FIG. 4 is a simplified schematic block diagram of a timing unit whichmay be used in conjunction with the embodiment of the inventionillustrated in FIGS. 2 and FIG. 5 isa diagram illustrating a mode ofcyclically timing the apparatus of the embodiments of FIGS. 2 and 3; and

FIG. 6 is a perspective representation of a preferred fluid reservoir.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to FIG. 1, a bloodanalysis system 20 which may incorporate the precepts of the presentinvention includes one or more withdrawal units 22, an analysis unit 24and a timing unit 26, which may be included within a calculation unit 28(not shown) if desired, or may be provided separately as shown herein.Even though more than one withdrawal unit may be used, on a consecutivebasis, to deliver blood to the analysis unit, physical isolation, asexplained more thoroughly hereinafter, avoids cross contamination. Thecalculation unit 28 may include indicators 30 if desired, or these maybe provided separately, such as at an intensive care unit nurses stationor other remote location. The calculation unit 28 may, if desired.comprise a blood analysis calculation unit of any type heretofore knownin the art, there being a plethora of such units available in themarketplace for bench testing of blood samples. On the other hand, thecalculation unit 28 may comprise a computing system, such as a largescale computer which may be time shared with other functions, or aminicomputer dedicated to operation with a withdrawal unit 22 and ananalysis unit 24 of the type disclosed herein. In the event that thecalculation unit includes a multi-function computer of some sort, thetiming functions may be readily provided thereby, rather than by adiscrete timing unit 26 of the type described with respect to FIG. 4hereinafter. It should be understood that the apparatus which providesthe timing and calculation of test results is not germane to the presentinvention; instead, the present invention is concerned with theimprovements in the withdrawal unit 22 as described with respect to FIG.2 hereinafter and in the analysis unit 24 as described with respect toFIG. 3 hereinafter, and with the timing of functions performed therebyso as to achieve new and improved operational functions and results.

Referring now to FIG. 2, a fitting-32, which may be of the well knownLuer type of fitting, is adpated for connection with a suitablearterial, venous, or umbilical catheter 33 of any type known for use influid communication with the blood system of the patient. The fitting 32is connected by tubing 34 to an oximeter 36 which is provided withelectrical inlet connections 38 and electrical output connections 40.The tubing 34 must be essentially impervious to diffusion of gas toprevent or minimize O and CO losses. KEL-F and nylon tubing have provedsatisfactory. The oximeter 36 may be of any well known type whichtypically measures oxygen saturation. The oximeter 36 is calibrated withsaline in the tubes of the withdrawal unit which remains there and isused as the medium for displacing blood within the withdrawal unit. Theappearance of a stable blood/saline interface at the oximeter terminateswithdrawal thereby minimizing the amount of blood removed. The blood isreturned to the patient, as hereinafter more fully explained. Thisprocedure allows more frequent examination of blood. If a stableblood/saline interface does not appear at the oximeter during withdrawalafter a predetermined time, withdrawal ceases as constant volume pump140 only cycles once.

The oximeter 36 is connected by tubing 42 to a fitting 44 and by meansof additional tube 46 to a pair of air detectors (AD) 48, 50. The airdetectors 48, 50 include and electric signal input 52 and respectivesignal outputs 54, 56. It is to be noted that the air detector outputterminals 54, 56 are depicted in a circular configuration in contrastwith the square configuration of the oximeter output terminals 40. Thisis to distinguish between electrical signals which are used directly inthe control of the system of the present invention (such as signals atthe terminals 54, 56) which are depicted in round configuration, fromoutput signals which are used externally of the system so as to deriveinformation relating to blood which is being tested (such as signals atthe terminals which are depicted in the square configuration. The airdetector is connected by tubing 58 to a port 60 of a fluid valve 62which,

along with similar other valves herein, is depicted schematically as ablock having a pair of solid lines illustrating fluid paths 64, 66 whichare normally connected or conductive to fluid when the valve is in itsnormal or deenergized, state, along with dashed lines depicting flowpaths 70, 72 which are normally not connected and not conductive tofluid when the valve is in its normal, deactivated, or deenergizedstate. Thus, the port 60 is connected by the path 64 to a port 74 and aport 76 is connected by path 66 to a port 78 when the valve isdeenergized as shown in FIG. 2. On the other hand, ports 60, 78 areinterconnected by the path and ports 74, 76 are connected by the path 72when the valve is activated or energized in response to an electricsignal applied at a terminal 80a. It should be noted that the ports 60,74, 76, 78 may act either as inlets or outlets without regard to whetherthe valve is in its operated or unoperated state. The valve 62, alongwith other similar valves herein, is designed to be resiliently urgedinto the inactivated state by a suitable means such as a spring so thatall flow will stop in the event of a power failure, or in the event ofdetecting air in the blood by the air detectors 48, 50 (in a manner tobe described hereinafter). The valve 62 (and other similar valves) maybe a pneumatically actuated valve, the pneumatic actuation in turn beingin response to an electrically operated solenoid valve. Valves of thistype are made by several manufacturers and are available in themarketplace.

The port 74 is connected by tubing 82 to an I.V. source and pumpapparatus 84 which may be of any conventionel type used for irrigationand/or infusion purposes. With the valve 62 deenergized as shown in FIG.2, the I.V. source and pump 84 is connected through the valve 62, theair detector 50, the connector 44 and the oximeter 36 to the collector32 for fluid communication with a catheter. When valve 62 is energized,blood is withdrawn from the patient and I.V. solution from 84 isexhausted to waste through port 76 and conduit 112. In this way nodamage to the system results which would otherwise threaten because ofpressure forces. The I.V. source and pump 84 may be used to infuseintravenous solution into the patient through the catheter at 32.

The air detector 48 is connected by tubing 86 to a port 88 of a valve90, another port 92 of which is connected by tubing 94 to the port 78. Aport 96 is connected by tubing 98 to a pressure transducer 100, a singlepath valve 102, and a flow restrictor 104. The valve 102 may be actuatedat 103 to conduct fluid by manual application, so as to use the salinesource 110 with a high flow rate for flushing out various lines.However. this forms no part of the invention herein, except toillustrate the versatility thereof. The pressure transducer can be ofany type well known for the purpose of deriving the patients bloodpressure, and provides an electricalsignal indicative thereof at anoutput terminal 106. This signal may be utilized in any well knownfashion, and the transducer forms no part of the present invention. Thevalve 102 and flow constrictor 104 are connected by tubing 108 to an 8psi saline solution source 110. With the valve 102 closed as shown, theflow constrictor 104 will provide a very minute, constant, low-pressureflow of saline to the tubing 98 which may be used as a constant flushsystem to prevent clotting at the end of the catheter connected to theconnector 32 during prolonged use, between withdrawal cycles. It shouldbe noted that this function of the apparatus is unnecessary whenirrigation is being regularly provided from the I.V. source 84, asdescribed hereinbefore. Therefore, the saline from the source 110 isnormally passed by valves 90, 62 through the port 76 and a suitablemeans 112 to waste. The means 112 may comprise tubing leading to a wastebucket, or it may simply comprise a syringe attached directly to theport The valve 90 includes a port l14'connected by tubing 116 to a port118 of a valve 120, which includes a port 122 connecting with a means124 leading to a blood cup which is described hereinafter with respectto P16. 3. The means 124 may otherwise comprise tubing leading to anyreceptacle for blood, or a syringe to receive blood which may beattached directly to the port 122. The valve also includes a port 126leading to tubing 128 which is provided in sufficient length (such as byinclusion of loops 130 therein) to serve as a reservoir on the order oftwo milliliters in capacity. The other end of the tubing 128 isconnected to a port 132 of a valve 134 which includes a port 136connected by tubing 138 to a constant volume pump 140. The exact natureof the constant volume pump is immaterial to the present invention withthe exception of the fact that if the pump 140 provides a constant knownvolume of fluid per unit of time that it is actually actuated, thevolume displacement for a complete stroke also will be constant.However, the pump 140 may comprise a syringe driven by a piston within acylinder, the piston in turn being driven by air supplied thereto overtubes 142, 144 under control of a valve 146 which is connected by a tube148 to a source 150 of air at psi (for instance). The valve in turn isresponsive to an OR circuit 152 so that it will be actuated in responseto signals applied on a terminal 154 or on a terminal 156.

With the valve 146 deactivated as shown, air is applied over the tube144 to cause a cycle which pushes blood from the source 140; when the ORcircuit 152 is energized by a signal on either of the terminals 154,156, it activates the valve 146 to apply air pressure from the source150 to the tube 142 and cause a cycle which draws fluid into the pump140. The valve 120 may be activated by a signal from an OR circuit 158in response to electric signals at either of two terminals 160, 80c.Provision of the OR circuits 152, 158 permits operation of the pump 140and the valve 120 in response to diverse controls; similarly, the valve134 is actuated in response to an electric signal from an OR circuit 162which in turn may operate in response to electrical signals applied oneither of two terminals 164, 80d, in a manner which is described indetail hereinafter with respect to FIGS. 4 and 5. Briefly, by actuatingthe valves 62, 90, 120 and 134 by the simultaneous application ofelectric signals to terminals 80a, 80b, 80c, and 80d, the

air detector 50 (and therefore a catheter connected tothe connector 32)will be connected to the pump 140, and the LV source 84 will be ventedthrough the path 72 to waste. This enables making a short stroke withthe pump 140 so as to draw blood into the oximeter 36 for the purpose ofmonitoring blood oxygen saturation, which can be done frequently withsubstantially no blood loss or interruption of any other functions; sucha test is extremely useful, when performed on a frequent, cyclic basis,to provide an indication of when a more complete blood analysis may berequired.

The valve 134 includes a port 132 connected by tubing 128 to a salinereservoir 130; this is used, as is described more fully hereinafter withrespect to FIGS. 4 and 5, to aid in the withdrawal of blood from (andreturn of a portion of the blood to) the patient, the insertion of someof the blood in the blood cup for analysis. and in washing out thesystem. Preferably, the reservoir 130 takes the form shown in FIG. 6,i.e., a constant diameter small bore tubing 128 coiled as at 130 about asuitable retainer such as the cylindrical retainer 171. The tubing 128presents a female port 173, through which additional saline may beintroduced to replenish the supply. This configuration has been found tosolve the heretofore substantial problem of blood/fluid interfacemixing. By restricting the blood/saline interface, infused saline isminimized.

The valve 134 also has a port 172 which is shown connected to aconnector 174 having a plug 176 therein. The port 172 may advantageouslybe used with a manual flush syringe, if desired.

The valve 120 is provided with an additional port 178 which is connectedto connector 180 blocked off by a plug 182. The connector 180 may beused to facilitate connection to the valve 120 of pressure transducerapparatus and saline flush apparatus similar to the apparatus 98-110described hereinbefore. With such an arrangement, constant flush may beprovided through the valves 90, 120, when deenergized as shown, andthrough the air detector 48 to the catheter connected to the connector32. Then, if desired, a second catheter may be connected to theconnector 44 (disconnecting the tube 46 from the tubing 42) so as toallow the running of two systems simultaneously, the catheter connectedto the connector 44 being operable either in conjunction with a constantsaline flush or in conjunction with an IV. irrigation. as describedhereinbefore. in dependence upon the setting of the valve 62. Thisillustrates the versatility of the present invention.

It is sometimes desirable to fit the influent end of the withdrawal unitwith an alarm, so that when blood unexpectedly appears, the attendant ispromptly notified. Such an alarm would be shut off during intentionalwithdrawal of blood.

Referring now to FIG. 3, an embodiment of an analysis unit 24 inaccordance with the present invention includes a blood cup which mayreceive blood manually from a syringe, or by being properly disposed mayreceive blood by other means 124 (FIG. 2) from one withdrawal unit. Theblood cup 190 represents a distinct interface between the withdrawalunit and the analysis unit permitting blood to reach the analyzer byforce of gravity but preventing analyzer fluids from reaching thepatient by maintaining a distinct physical separation between the units.Thus, the analyzer fluids (calibration gases and liquids) and thecomponents of the analyzer need not be sterile. As a result allconstraints required by a sterile analyzer are removed and the analyzermay be used on one patient after another without appreciable time delay.

In addition, the blood cup 190 may receive a water washout solution overtubing 192, and either of two buffer solutions over tubing 192, 194. Thetubing 192-194 is connected to respective check valves 196198 which arein turn connected by respective tubing 200-202 to additional checkvalves 204206 and to corresponding syringe pumps 208210. The pumps208-210 provide a push stroke in response to electric signals applied tocorresponding terminals 212214. The volumetric capacity of the pumps issuch that upon release of the signals on terminals 212-2l4 the pumpsprovide draw cycles through the check valves 204-206 to supply thedesired amount of fluid to be driven through the check valves 196-198upon the next energization of the pumps by the application of electricsignals at the terminals 212-214. The check valves 204-206 are connectedto a source 216 of water and to sources 218, 220 of two different buffersolutions. The buffer one solution in the source 218 may comprise adilute solution of Na HPO and KH and P0 having a pH of about 7.45, andthe buffer two solution in the source 220 may be a dilute solution of NaHPO, and KH P0 having a pH of about 6.88. The two different pHs allowfor two calibration points on a pH test as described hereinafter.

The blood cup 190 is connected by tubing 222 to a port 224 of a valve226 which alternatively connects the blood cup 190 to tubing 228 of a pHtester 230 and through tubing 232 connected to a blood gas tester 234.An important feature of the present invention, which is described morefully with respect to FIGS. 4 and 5 hereinafter, is the utilization ofthe pH tester 230 to check the blood gas tester 234 for leaks. In orderto achieve this, a means 236 is provided to insure that the liquid inthe tubing 228 and in the tubing 232 are at the same electricalpotential. The means 236 illustrated in FIG. 3 may comprise a stainlesssteel wire which passes through the walls of the respective tubing 228,232 so as to provide for an electrical conduction therebetween. On theother hand, depending on the nature of the valve 226, it is possiblethat in some utilizations of the present invention the electricalconductivity can be maintained by means of wetness of the surfaceswithin the valve 226, with regard to whether the valve is actuated ornot. The tube 228 provides fluid connection to a pH electrode 238 whichmay be of any conventional known type that provides an electric signalat an output 240 which, in conjunction with a reference electrode signalat an output terminal 242 provides a measure of the pH of the fluidtherein. The electric output terminal 242 is connected to a referenceelectrode 244 of the type known in the art, which may be connected bytubing 246, or in any other suitable fashion, to the primary electrode238. The reference electrode 244 is connected by tubing 248 to a blooddetector 250 which may be of any conventional type, such as aphotodetector system which senses the opacity of the fluid therein,thereby recognizing the difference between blood and either gas orsaline solution. The blood detector 250 is provided with an electriccurrent applied over an input terminal 252 to operate a light sourcetherein, and the photo-detector therein provides an electric signal atan output terminal 254 which is a measure of the transmissivity of thefluid flowing therein. Since this is of conventional nature and forms nopart of the present invention, further description is not given herein.The sensing of the blood/fluid interface at blood detector 250 and/orblood detector 268 controls the positioning of blood which is pulledfrom the cup and accordingly, the needed volume of blood. If blood isnot sensed within a predetermined time, an error is indicated,measurement is terminated and the system is flushed. In thisway theamount of blood used by the analyzer and not returned to the patient isminimal. The blood detector is connected by tubing 256 to a port 258 ofa valve 260 which is always operated in conjunction with the valve 226by simultaneous application of electric operating signals to a pair ofinput terminals 262a, 262b, as is described more fully hereinafter.

The tubing 232 is connected to gas electrodes 264 which provide electricsingals at a pair of output terminals 267, 268. The gas electrodes maybe conventional membrane-type electrodes for measuring P0 and PCO andform no part of the present invention. The gas electrodes 264 areconnected by tubing 266 to a blood detector 268 which is similar to theblood detector 250 including an electric input terminal 270 and anelectric output terminal 272. The blood detector 268' is connected bytubing 274 to another port 276 of the valve 260. When deenergized, thevalve 226 provides flow of blood from the blood cup 190 into the bloodgas detector 264 and through the port 278 to port 279 of a pump valve280. When energized, the valve 226 connects the blood cup 190 to the pHtester 230 and connects the gas detector 234 through a port 282 totubing 284 or other suitable waste disposition means. When the valve 226is energized, the valve 260 is also energized, connecting the pH tester230 through the port 258 of valve 260 to port 279 of the pump valve 280,but also connecting the gas tester 234 through ports 276 and 286 ofvalve 260 to a port 288 of a calibration gas valve 290 by a tubing 291.The pump valve 280 includes a port 292 connected to a constant volumepump 294 and a port 296 connected by a suitable tubing 298 or othermeans to a proper disposition for liquid waste.

The port 288 of the valve 290 is normally connected through a port 302and tubing 304 to a flow constrictor 306 which in turn is connected bytubing 308, a valve 309 (operated by a signal at a terminal 310). andtubing 311 to a source 312 of a high P0 and PCO The tubing 308 alsoapplies such to a variable flow constrictor 313 which is provided with amanual adjustment 314 to adjust the amount of flow therethrough. Thisprovides gases from the source 310 to the water source 216 over tubing316, thereby to provide sufficient carbonate in the water of the source216 so that the gas electrodes 264 will, after being washed with waterfrom the source 216, have a substantial carbon dioxide concentrationdiffused through the membranes prior to a final calibration gas to drivewashout water through the unit, the concentrations will not be sodepleted in the gas electrodes 264 so as to require an undueequilibration time for a final test after all blood is washed therefrom.

The valve 290, when activated by an electric signal at an input terminal320, connects its port 288 with a port 322 and tubing 324 to anotherflow restrictor 326 which is connected by tubing 328 to a source 330 oflow P0 and PCO Since the sources 312, 330 are under pressure, they areused, as described hereinafter, in the process of cleaning out the gaselectrodes 264. The analyzer is calibrated before blood is introduced.Specifically, a liquid calibration fluid is used to calibrate pHelectrode 238 and a gas calibration fluid is used to calibrate gaselectrodes 264. Thereafter, the calibration fluids are retained in theanalyzer and used. responsive to negative pressure, to displace bloodwithin the analyzer after it is received at cup 190. In this way thecalibration is preserved.

Referring now to FIG. 4, the timing unit 26 includes some source ofordinary power 340 which is assumed to include means 342 for turning iton and off. Such power may simply comprise cycle 120 volt power. Thesource 340 is connected by a line 344 to a onesixth revolution perminute motor 346 through a normally open switch 348 and a line 350. Theswitch 348 is normally open and must be activated by a signal on a line352 from an OR circuit 354 in order to apply power from the line 344 tothe motor 346. The motor is connected by shafts 356, 357 to a one trackrotary timer 358 and a sixteen track rotary timer 359. The timers 358,359 are supplied power from a valve power source 360 over a line 361.When it is desired to run the withdrawal unit for periodic oximetertesting only. an oximeter ON switch 364 may be closed applying powerfrom the line 361 to a set input of a latch 365 which provides a signalon a line 366 to operate the OR circuit 354 and apply power to the motor346. At the same time, the signal on the line 366 applies power to theterminal which in turn is applied in FIG. 2 to all of the terminals80a80d. This connects the constant volume pump 140 (FIG. 2) through thevalves 62, 90, and 134 to draw blood through the air detector 50 and theoximeter 36 for the purpose of testing the oxygen saturation of theblood. Within the one track timer 358, a single contact element perrevolution is provided, so as to provide a signal on a line 368 to theterminal 154 which will cause the OR circuit 152 (FIG. 2) to operate thevalve 146 and initiate a short stroke of the pump 140. For instance, thelength of the signal on the line 368 (and therefore the length of timeduration of the pump stroke) may be approximately eight seconds so as todraw approximately 0.5 of a milliliter of blood through the oximeter 36,and then restore it back to the patient. This is readily achieved byproviding a contact in the timer 358 which extends over 8 (the samenumber of degrees as is desired seconds since the one-sixth rpm motor346 will cause the timer to complete one revolution in 360 seconds 6minutes). Be-

cause of its simplicity, the internal structure of the timer 358 has notbeen shown. Once the switch 364 is closed, the testing of the blood inthe oximeter will continue cyclically until it is desired to cease,which is achieved by depressing an oximeter OFF switch 370.

This causes an OR circuit 372 to reset the latch 365 so as to removepower from the line 368, thereby deenergizing the terminal 80 to returnthe valves in FIG. 2 to their unenergized state, and causing the switch348 to resume its normally open condition so that no more power isapplied to the motor 346.

Additionally, the OR circuit 354 may be operated by a signal on a line374 in response to the setting of a bistable device such as a trigger orlatch 376 whenever full automatic withdrawal and analysis cycles arebeing performed under the control of the l6-track rotary timer 359. The16-track timer 359 has l6-tracks of contacts which are arranged as shownin FIG. 5. If the timer 359 is a drum timer, then FIG. depicts thecontact arrangement simply by joining the left end thereof (zero secondsin time and zero arcuate degrees) with the right end thereof (360seconds in time and 360 arcuate degrees). On the other hand, if thesixteen track timer 359 is arranged in the form of a disc. then it maybe profitable to provide on the radially inward tracks those contactswhich are very small and do not consume much space whereas the largercontacts, or ones that have to be extremely accurate, may be placed onthe radially outward tracks, all as is well known in the rotary shaftencoder art. Power to the contacts within the timer 359 is supplied bythe line 361. Starting a full withdrawal and analysis cycle is achievedby setting the latch 376 by means of depressing a START button 380,which will cause the latch 376 to remain energized until the end of thecomplete cycle, which occurs at about 355 seconds after initializing bythe generation on a motor control line 381 of a signal which indicatesthat the cycle is complete. This is applied to an OR circuit 382 whichcauses resetting of the latch 376. The OR circuit 382 will also beoperated by an OR circuit 384 in response to signals at either of a pairof terminals 54, 56 (FIG. 2) indicating that air bubbles have beendetected in the blood lines. The OR circuit 384 may also operate analarm 396 so as to advise an attendant at an intensive care nursesstation or otherwise that air has been detected in the lines. While therotary timer 359 is operating, it presents signals on a plurality oflines to operate valves and pumps so as to cause direct cyclic operationof both the withdrawal unit and the analysis unit for a completeautomatic withdrawal and sampling of blood, together with washout andcalibration thereof. Each of the lines at the output of the rotarytimer, depicted as being within a trunk of fifteen lines 398, isprovided with an appropriate legend, and is connected to the electricterminal which it operates in FIGS. 1, 2 or 3.

Specifically, the signal lines 398 from the sixteen track timer 359include a signal causing a test of the air detectors on a line 399,which operates a normallyopen switch 400 to shortcircuit a resistor 402,so as to provide more current from an LED power source 404 through theterminal 52 to the air detectors 48, 50

(FIG. 2). This over-powers the air-detectors and forces an alarmcondition even though there is liquid in them. unless they areinoperative.

The air detector and its operation form no part of the presentinvention; however, it should be obvious that combination of the signalon the line 52 and a lack of signals on the lines 54, 56 could operatean OR circuit similar to the OR circuit 384 to create an alarm conditionwhich could turn off the latches 365 and 376 and operate the alarm 396if the air detectors are not working. A withdrawal pump signal whichcauses the withdrawal pump 140 (FIG. 2) to initiate a pull stroke.thereby drawing blood into the system from a catheter, is provided tothe terminal 156. A withdrawal pump valve signal at terminal 164operates the valve 134 (FIG. 2) in such a fashion as to connect the pumpto the 2 milliliter reservoir 130. A blood cup valve signal applied to aterminal 160 causes the valve (FIG. 2) to operate so as to connect the 2milliliter reservoir the patieint (port 118) rather than to the bloodcup. A sample pI-I signal is applied to a terminal 410 to indicate toany apparatus, such as the calculation unit 28 of FIG. 1, that now isthe proper time to sample the output of the pH tester 230 (FIG. 3) atthe terminals 240, 242. Similarly, a sample gas signal is applied to aterminal 412 to indicate to the calculation unit 28, or such other unitas may be used to analyze the results of blood tests, that now is theproper time to sample the output of the gas tester 234 at the terminals267, 268. A gas/pH valve signal applied to the terminal 262 in FIG. 4 isconnected to both of the terminals 262a 2621) (FIG. 3) so as to causesimultaneous operation of the valves 226, 260 so as to transfer primaryoperation from the gas side to the pH side. A buffer one pump signalapplied to a terminal 213 causes the buffer one syringe pump 213 tostroke in the push direction. A high concentration calibration gassignal applied to a terminal 310 causes closure of the valve 309 (FIG.3) to allow the high concentration calibration gas source 312 to enterthe system. The calibration gas valve signal applied to a terminal 320causes the valve 290 (FIG. 3) to transfer from the normal highconcentration connection, as shown. to connect the low concentrationsource 330 with the port 288. An H O pump signal connected to a terminal212 causes the syringe pump 208 (FIG. 3) to initiate a push stroke. Abuffer two pump signal applied to a terminal 214 causes the syringe pump210 (FIG. 3) to initiate a push stroke. A gas blood detector signalapplied to a terminal 270 powers a light source in the blood detector268' (FIG. 3) so as to be able to detect the presence of blood.Similarly, a pH blood detector signal applied to a terminal 252energizes the blood detector 250 (FIG. 3) so as to be able to detectblood passing therethrough.

An analysis pump signal is applied to a terminal 414 for application tothe valve 280 (FIG. 3) and to a related valve 416 which is connected inan obvious fashion by tubings 418, 420 to the pump 294. Thus, with thesignal present at the terminal 414 the valve 280 will connect the valve260 to the pump 294, and the valve 416 will cause the pump 294 toinitiate a pull stroke pulling fluid through the valve 292 into the pump294; at this time, operating air within the pump is exhausted throughthe tube 418 and the valve 416 through a port 422 to exhaust. Uponremoval of the signal on the terminal 414, the valve 280 connects theport 292 with the port 296 and the valve 416 drives air through the tub-The signal on the terminal 414 is generated specially in FIG. 4 by meansof an AND circuit 426 in response to an OR circuit 427 operated byeither one of two OR- invert circuits 428, 430. These circuits arenormally operative because there is normally no signal present at theterminals 270, 252 so that the blood detectors are inoperative, andthere is also no signals at their output terminals 254, 272. However,once the blood detectors are activated by signals at terminals 252, 270these signals preclude the OR-invert circuit 428 from any longerproviding a signal to the OR circuit 427. But if no blood is detected inthe blood detectors, then there will still be no signals at the blooddetector output terminals 254, 270 .(FIG. 3) so that the relatedOR-invert circuit 430 will operate the AND circuit 426 to provide asignal at the terminal 414 for the operation of the pull stroke of theanalysis pump 294 (FIG. 3). However, once blood is sensed by either ofthe blood detectors, a signal on either of the terminals 254, 272 willcause the OR-invert circuit 430 to remove the input to the OR circuit427, thus terminating the stroke of the pump 294 (FIG. 3). Use of the ORinvert circuit 428 precludes the possibility of noise or other spurioussignals from blocking the AND circuit 426 when the blood detectors arenot turned on. This feature allows drawing just a requisite amount ofblood into the pH tester 230 and the gas tester 234 so the blood isntdrawn through other parts of the system thereby necessitating a greateramount of blood and washout.

Operation of the device, as illustrated in FIG. 5, begins with the mainpower source turned on by the depression of the start switch 380 (FIG.4) which will cause the latch 376 to become set, overriding a tendencyof the OR circuit 382 to reset it, thereby closing the normally openswitch 348 so as to apply main power to the one-sixth rpm motor 346. Theswitch should be depressed for at least a second until the motor canturn sufficiently so as to clear the motor control segment and thusremove the signal on the line 381 so that the motor will continue torun. Then, at time zero, signals are applied to the terminals 213, 310,414 and 262 so as to energize the buffer one pump, close the highconcentration gas valve, start the analysis unit pump 294 and place thegas/pH valve to the pH side. This causes buffer one to be pushed intothe blood cup 190 and drawn by the constant volume pump into the pHtester 230 all the way into the pump 292, while high concentrationcalibration gas flows into the gas tester 234. All of these signalsremain present for seconds.

I However, after the first second, the air detectors in the withdrawalunit (FIG. 2) are tested. Thereafter, at the twenty-first second,signals are applied to terminals 156, 164 and 160, and the pump in thewithdrawal unit (FIG. 2) is actuated at the same time that the pumpvalve and cup valve are actuated so as to draw blood from the catheterthrough the connector 32 through the oximeter and the air detector intothe port 88 of valve 90 through the valve 120 and into the 2 milliliterreservoir 130. These conditions are maintained for 40 seconds, untilabout the sixty-first second, although the pump valve 134 is left in theactuated position to connect the 2 milliliter reservoir to the pump allthe way to the one hundred first second. While the blood is being drawninto the withdrawal unit. at about the twentieth second, all of theelements in the analysis unit are turned off and there is a 10 secondequilibration period where buffer one is allowed to equilibrate withinthe pH tester 230. Thereafter, at about the fortieth second. the pH issampled at the terminal 240 so as to provide a first calibrationmeasurement of the pH detector 230. As soon as this is complete. atabout the forty-fist second. buffer one is flushed out of the pH tester230 by energizing the water pump (terminal 212), reactivating the gas/pHvalve so as to feed pH (terminal 262), and reactivating the pump(terminal 414) for a full cycle so that as water or saline falls intothe blood cup, it is drawn all the way down into the pump. These signals(terminals 212, 262 and 414) are maintained energized for about 20seconds until about the sixtyfirst second.

At the sixty-first second, in the withdrawal unit. the signal onterminal 156 and that on terminal 160 are removed so that the withdrawalpump will initiate a-push stroke with the valve deenergized so thatblood is pushed from the 2 milliliter reservoir into the blood cup. Atthis time. everything in the analysis unit is deenergized and remains sofor approximately 10 seconds to allow theblood to settle down in theblood cup. The valve 120 is actuated after about 7 seconds (whichpermits pumping substantially 0.4 milliliters into the blood cup) andthen it is energized so that the remainder of the blood will be returnedto the patient along with approximately 1.5 milliliters of saline. It isto be noted that, prior to starting the operation, saline existed in thelines as a result of initially loading them or as a result of finishingthe prior cycle as is described hereinafter.

After allowing ten seconds for the blood to settle in the cup, at aboutthe seventy-first second, the blood detector 250 is turned on by asignal on terminal 252, and blood is drawn into the pH tester byapplying signals to the terminals 262 and 414 so that the gas/pH valveis in the pH position and the pump will initiate a pull cycle. However,as soon as blood reaches the blood detector 250, it will cause (by meansof the apparatus at the bottom of FIG. 4 described hereinbefore) deenergization of the signal at the terminal 414 so that the pump stroke stopsimmediately. This prevents pulling any unnecessary amount of bloodbeyond the reference electrode 244; This will occur in something on theorder of 8 seconds, and at the end of ten seconds the blood detectorvalves 226 and 260 and the primary initialization signal for the pump292 are all deactivated. This occurs at approximately the eighty-firstsecond. Then 20 seconds of equlibration time is allowed to elapse.During this time, the remainder of the blood in the analysis unit hasbeen returned to the patient; it should be understood that since thepump is a constant volume pump, regardless of the energization thereof,the volume of fluid to be returned to the patient is determined simplyby the length of stroke so that the pump and relay circuits in thewithdrawal unit are energized simply for a long enough period of time toallow the pump to complete its stroke. This occurs at approximately theone hundred and first second.

At this time, the blood in the pH tester 230 is still equilibrating, asis the high concentration calibration gas which entered the gas tester234 at time zero. At

the one hundred and first second or so, the pump in the withdrawal unit(FIG. 2) is caused to make a pull stroke with the valve 134 disenergizedto pull saline solution from the source 170 down into the pump. At thesame time (one hundred and first second) the pH and gas detectors areboth sampled at the output terminals 240, 242 and 267, 268. Thiscomprises a first test of the pH of the blood itself and a firstcalibration test of the gas electrodes 264. Following that, at the onehundred and second second, the gas blood detector 268' is turned on witha signal at the terminal 270 and the pump is started by applying asignal on the line 414. This action draws blood from the blood cup 190down through the gas tester 234 until the blood reaches the blooddetector at which time a signal appears on terminals 272 which, throughthe apparatus at the bottom of FIG. 4, removes the signal on line 414and stops the blood pull stroke. Then there is a 45 second equilibrationperiod where everything in the analysis unit (FIG. 3) is turned off.However, at the one hundred and twenty-first second, flushing of thewithdrawal unit (FIG. 2) begins by shutting off the signal on line 156to the pump so that the pump will commence a push cycle and energizingthe valve 134 so that the push will be in the direction of the 2milliliter reservoir 130. This starts saline (which has just beenwithdrawn from the reservoir 170) to flow through the two milliliterreservoir 130 and through the deenergized valve 120 into the blood cupor waste receptacle. However, after ten seconds, the valve 120 isenergized so that the remainder of the saline then flows upwardlythrough the valve 90, the air detector 48 and oximeter 36 toward thecatheter. This insures that the lines in the withdrawal unit are leftwith saline in them (as referred to hereinbefore).

Following a 45 second equilibration period with blood in the gasdetector 234, both the gas and pH are sampled at their terminal 240, 242and 267, 268 which comprise the first sampling of gas in the blooditself and the second sampling of pH in the blood. The second samplingof pH is to provide an indication of the integrity of the gas electrodes264; if there is any leakage in the gas electrode 264, such a leak wouldcause a change in the electrical potential of the blood in the tubing232, the because of the stainless steel electrical connector 236 betweenthat tubing and the tubing 228, it would also result in a change in theelectrical potential of the blood within the pH electrode 238. Thiswould result in a different pH reading than that which was previouslyobtained. Utilization of a second pH reading of the blood is achieved bycalculations performed in the calculation unit 28 (HO. 1) or in acomputer if one is used, or simply a substantial difference in pHreading indicates to the operator that there is likely to be a fault inthe gas electrodes 264. This is an important feature of the presentinvention.

After sampling the pH and gas electrodes, at about the one hundred andfifty-sixth second, flushing of the blood from the pH tester 230 and thegas tester 324 commences. This is achieved by closing the high gas relay309, energizing the high/low gas valve 290 so that the low concentrationcalibration gas is available, energizing the gas/pH valves 226 and 260so as to permit flow into the pH side and starting the pump by applyinga signal to the terminals 414. The high gas valve 309 is closed topermit leakage of gas from the source 312 into the water source 216 soas to increase the carbon content thereof. At the same time, saline isdrawn from the blood cup down into the pH tester 230. These conditionscontinue until about the one hundred and seventy-sixth second. At thattime, the high gas valve 309 is closed and the pump is turned off sothat it makes a push stroke with the valve 280 deenergized, pumpingblood and perhaps some saline to liquid waste through the port 296.After two seconds (at the one hundred and seventy-eighth second), thepump is again turned on drawing more saline into the pH tester 230;during this entire period of time (from the one hundred and fifty-fifthsecond) the low concentration calibration gas in the source 330 has beenpassing through the valve 290 and the valve 260 upwardly through the gastester 234 and through the valve 226 upwardly through the port 282driving blood to waste. At about the one hundred and ninety-eighthsecond the pump is again shut off for 2 seconds and it pushes the bloodand saline which it has drawn from the pH tester 230 outwardly throughthe port 296 of the valve 280 to waste. At the two hundredth second, theH 0 pump is again energized (212) to cause water to be pushed into theblood cup. The analysis pump is again started at about the two hundredthsecond and again draws saline and water through the pH detector forthree seconds, then the valves 226 and 260 are turned off for 2 secondsso that the pump, instead, draws saline and water into the gas detector234. After two seconds the valves 226 and 260 are again energized sothat saline is drawn into the pH detector, and while this is occurring.the low concentration calibration gas in the source 330 pushes some ofthe saline out of the gas detector 234 upwardly through the port 282 toliquid waste. This process continues until about the two hundred andtwentieth second when the pump is turned off so that it provides a pushstroke to push all the waste it has collected from both the pH tester230 and the gas tester 234 outwardly through the port 296 to waste. Theprocedure is again repeated so that at approximately the two hundred andforty-second second the pump again discharges waste that it hascollected from both the pH tester 230 and the gas tester 234, duringwhich time the valves 226 and 260 have cycled, and while in theenergized position the low concentration calibration gas of the source330 has pushed waste upwardly out of the gas tester 234. At about thetwo hundred andforty-fourth second, the pump and the pH/gas valve areagain turned on at the same time as the buffer number two pump is turnedon so that buffer number two begins to be pumped into the blood cup 190and this is drawn into the pH tester 230. This is completed 20 secondslater, at about the two hundred and sixty-fourth second. During thistwenty second period, the low concentration calibration gas of thesource 312 has been continuously running into the gas tester 234 andventing outwardly through the port 282 to waste. Thus at the two hundredand sixty-fourth second, the pH tester 230 is filled with buffer numbertwo and thegas tester 234 is filled with low concentration calibrationgas from the source 330. An equilibration period of 45 seconds thenpasses following which, at the three hundred and ninth-second, both pHand gas are again sampled at their terminals 240, 242 and 267, 268 for afinal calibration of both the pH and gas testers 230, 234. Thecalibration provides corrections for changes in sensitivity and drift ofthe electrodes.

All that now remains is to purge the calibration gas out of the gaselectrode and leave the gas electrode filled with water so as to preventthe membranes therein from drying out. It is to be noted that the pHelectrode is left with buffer number two residing therein which preventsit from drying out. The loading of water and purging of gas in the gaselectrode 264 is accomplished, beginning at the three hundred and tenthsecond, by energizing the water pump by means of a signal at theterminal 212 so as to commence to pump water into the blood cup 190 atthe same time that the pump is operated by providing a signal at theterminal 414 while leaving the valves 226 and 260 deenergized so thatthe clean water is drawn into the gas tester 234. After 20 seconds, thepump is deactivated for two seconds to allow dumping the mixture of gasand water out to liquid waste, following which it is again activated topump the remaining water out of the blood cup 190 into the gas tester234. This completes the operation of the cycle and the motor is causedto shut off at about the three hundred and fifty-fifth second bygenerating a signal on the motor control line 380 which activates the ORcircuit 382 to reset the latch 376, thereby removing the signal from thenormally open switch so that the motor no longer receives power. Themotor will therefore stop when the sixteen track rotary timer is set onthe contact that provides the motor control signal on line 381.

The embodiment of the invention described hereinbefore thus provides avery compatible blood withdrawal unit which, according to the invention,may withdraw blood through lines filled with saline so as to preservethe integrity of tests to be performed on blood, or may withdraw bloodthrough lines filled with l.V. irrigation solutions, thereby to minimizethe opportunity for sodium buildup in the patient. In addition, thedescribed embodiment provides for final calibration of gas and pHtesters after testing of blood, in addition to initial calibrationsbefore the testing of blood. By providing a dual test of blood pH, onewithout fluid in the gas detector and one with fluid in the gasdetector, together with providing for an electrical connection betweenthe gas and pH testers, the dual pH tests provide a measure of theintegrity of the gas tester. Carbonation of washout water in the gastester provides for the preestablishment of a certain level of carbonatein the gas detector to reduce the time necessary for equilibrationthereof, and in further accord with the invention, valving between thepH tester and the gas tester permits simultaneous washout utilizing asingle pump, in combination with the use of calibration gas tocompletely flush, forwardly and backwardly, the gas electrode, whilesimultaneously performing a forward flush of the pH electrode.

Although the invention has been shown and described with respect to apreferred embodiment thereof, it should be understood by those skilledin the art that various changes and omissions in the form and detailthereof may be made therein without departing from the spirit and thescope of the invention.

Having thus described typical embodiments of our invention, that whichwe claim as new and desire to secure by Letters Patent is:

1. An automated blood unit comprising: first and second fluid valves,each having a normal position and an operated position;

a first fluid path means adapted to be connected to an indwelling bloodcatheter for interconnecting said catheter with a first port of saidfirst fluid valve;

a second fluid path means connected to said first fluid path means andto a first port of said second fluid valve;

a third fluid path means interconnecting a second port of said secondfluid valve with a second port of said first fluid valve;

a reversible pump;

means for interconnecting said pump with a third port of said firstfluid valve;

said first fluid valve comprising first fluid communicating means, whenin its normal position. connecting said first fluid path means with saidpump, and also comprising second fluid communicating means when in itsoperated position. connecting said third fluid path means with said pumpvia the interconnecting means, and said second fluid valve comprisingfirst fluid communicating means, when in its operated position,connecting said second fluid path means with said third fluid pathmeans, so that, with a catheter connected (a), in response to said pumpinitiating a draw cycle with said first fluid valve in its normalposition, fluid is drawn by force of said pump along a pathwaycomprising said first fluid path means, said first fluid communicatingmeans of the first fluid valve and said interconnecting means therebydrawing blood from said catheter into said first fluid path means. and(b) in response to said pump initiating a draw cycle with said first andsecond fluid valves in their operated positions, fluid is drawn alonganother pathway comprising said second fluid path means, the first fluidcommunicating means of the second fluid valve and the third fluid pathmeans thereby drawing blood from said catheter into said second andthird fluid path means, and so that, in response to said pump initiatinga push cycle following said blood withdrawal into either of saidpathways,

blood is returned to said catheter along said pathways. 2. The automatedblood unit according to claim 1 additionally comprising:

an intravenous irrigation solution source connected to a third port ofsaid second valve, said third port being connected by second fluidcommunicating means to said second fluid path means when said secondvalve is in its normal position, a fourth port of said second fluidvalve and third fluid communicating means connecting said fourth port tosaid third fluid path means at the second portof the second valve whensaid second valve is in its normal position, said fourth port adapted todischarge to waste fluid passing from the third fluid path means andsaid third communicating means, said first fluid path being adapted tobe filled with saline solution, so that blood is withdrawn from saidcatheter into said first fluid path means due to negative salinepressure caused by the pump and thereafter returned to said catheterfrom said first fluid path means in response to positive fluid pressurecreated by the pump against the saline and thence against the blood whensaid fluid valves are in their normal positions, and blood is withdrawnfrom said catheter through the first fluid path means into said secndfluid path means due to negative saline pressure caused by the pump andthereafter returned to said catheter from said second fluid path meansalong said first fluid path means in response to positive fluid pressureof said intravenous solution when said pump is operated with said valvesin their operated positions.

3. The automated blood unit according to claim 1 wherein said firstfluid path means includes an oximeter disposed between the junction ofsaid second fluid path means with said first fluid path means and thepoint of connection of said catheter to said first fluid path means andwherein the oximeter comprises means for taking oximeter readings bypump drawing a small sample of blood along the first fluid path meansthrough the oximeter and then pump displacing at least a portion of theblood sample back along the first fluid path means into the patient.

4. The automated blood unit according to claim 1 ad ditionallycomprising:

a selectively disengagable connection means for connecting said secondfluid path means with said first fluid path means, said connection meansbeing adapted for connection to a second indwelling catheter in lieu ofthe first fluid path means.

5. The automated blood unit according to claim 1 additionallycomprising:

a low pressure constant flow saline source connected by fourth fluidpath means to a fourth port of said first valve, said first valvecomprising a third fluid communicating means which, when the first valveis in its normal position, connects said saline source with said thirdfluid path means, said first fluid valve also comprising fourth fluidcommunicating means which, when said first valve is in its operatedposition, connects said saline source with said first fluid path means,the second fluid valve comprising an additional port being connected byadditional fluid communicating means to said third fluid path means,when said second valve is in its normal position, said fourth portadapted to discharge fluid passing therethrough to waste, so that saidfirst fluid valve (a) connects said first fluid path means with saidpump via said first fluid communicating means of the first valve and theinterconnecting means and connects said saline source with waste viasaid third fluid communicating means of the first fluid valve, the thirdfluid path means, the additional fluid communicating means and theadditional port of the second fluid valve, when said first and secondvalves are in their normal positions, and (b) connects said salinesource to said first fluid path means via said fourth fluidcommunicating means, to act as a blood clot preventing flush for acatheter connected to said first fluid path means, when said first valveis in its operated position, said pump being simultaneously incommunication with said second catheter via the interconnecting means,the second fluid communicating means of the first valve, the third fluidpath means, the first fluid communicating means of the second valve andthe second fluid path means, said second valve being in its operatedposition.

6. The automated blood unit according to claim 5 including a bloodpressure transducer in fluid communication with one of said pathways.

7. A blood testing system comprising:

a catheter to be introduced through the skin into the cardiovascularsystem ofa patient using a sharp instrument; a blood withdrawal unitconnected to the catheter.

5 the blood withdrawal unit comprising a closed fluid storage systemcomprising fluid pathway means comprising flexible tubing, the pathwayhaving a uniform small bore throughout. which pathway means areinitially filled with biologically inert fluid, blood flow meansincluding two directional power means imposing positive and negativepressures upon the inert fluid within the pathway means for withdrawingblood, under negative pressure, through the catheter into and expellingall of the withdrawn blood from the withdrawal unit under positivepressure, said blood flow means compris ing means for causing at least asubstantial portion of the withdrawn blood to be returned through thepathway means and the catheter into the cardiovascular system undernegative pressure caused by said power means, whereby upon withdrawal ofblood through the catheter into the uniform bore pathway means of thewithdrawal unit said blood flow means causes little if any turbulentflow resulting in an essentially two dimensional blood/fluid interfacecomprising a negligible amount of fluid with little or no mixing ofblood and fluid and, thereafter, causing return of substantially allblood along the pathway means and into the cardiovascular system throughthe catheter and infusion into the cardiovascular system of very littleinert fluid under positive pressure caused by the power means.

8. An automated blood testing system comprising:

a catheter to be placed in the cardiovascular system of a patientthrough venipuncture;

a blood withdrawal unit comprising fluid passageway means in fluidcommunication with the catheter, biologically inert fluid in saidpassageway means, at

least one test station disposed at a site intermediate the passagewaymeans, and two way hydraulic pressure control means for removing bloodjuxtaposed the inert fluid through the catheter and along a pathcomprising said passageway means to said test station under hydraulicpressure at the same time withdrawing said inert fluid along the samepath thereby creating a movable interface between the blood and fluid;

said withdrawal unit further comprising means at said test station sitefor testing said blood disposed in said passageway means at said stationand means creating hydraulic pressure which acts upon said inert fluidto jointly displace the inert fluid and blood in a reverse directionalong said path and thereby return essentially all of said removed bloodto the patients cardiovascular system through the catheter, said two waycontrol means having means terminating the return of blood to thecardiovascular system when the blood/fluid interface is juxtaposed thecatheter.

9. An automated blood testing system comprising:

a plurality of sterile blood withdrawal units each withdrawal unitadapted to be coupled to a patient via a catheter placed through theskin into a vessel by a sharp instrument and each withdrawal unitdefining an independent blood flow path therethrough;

a single non-sterile blood analysis unit comprising one-way bloodingress means which receives blood from any selected one of saidwithdrawal units at any specified point in time, passageway meansconnected to the one-way blood ingress means, a plurality of bloodtesting sites disposed at various locations along the passageway means,each blood testing site comprising means for evaluating blood, means fordisplacing blood received at the one-way blood ingress means along thepassageway means to each testing site, and blood egress means forexpelling blood from the analysis unit to waste;

each withdrawal unit comprising means for removing blood from a patientthrough the associated catheter and flow path of the associatedwithdrawal unit to the one-way blood ingress means of the analysis unitand for returning blood to the patient which, following withdrawal, isdisposed within the flow path of said withdrawal unit between thecatheter and the one-way blood ingress means of the analysis unit.

10. An automated blood testing system comprising:

a sterile blood withdrawal unit adapted to be coupledv to a patient viaa catheter placed through the skin into a vessel by a sharp instrument,the withdrawal unit defining a blood flow path therethrough;

a non-sterile blood analyzer comprising a one-way blood ingressinterface in oneway communication with the blood flow path to receiveblood from the withdrawal unit, the one-way blood ingress interfacecomprising means preventing blood flow from the analyzer back to thewithdrawal unit, and passageway means connected to the one-way bloodingress interface, at least one blood testing site disposed at alocation along the passageway means, the blood testing site comprisingmeans for evaluating blood, means for displacing blood received from thewithdrawal unit at the one-way blood ingress interface along thepassageway means to the testing site, blood egress means for expellingblood from the analyzer to waste;

the withdrawal unit comprising means for removing blood from the patientthrough the catheter and flow path of the withdrawal unit to the one-wayblood ingress interface of the analyzer and for returning to the patientresidual blood disposed within the flow path of the withdrawal unitbetween the catheter and the one-way blood ingress interface.

ll. The system of claim 10 wherein the blood flow preventing means ofthe one-way blood ingress interface comprise a blood effluent tubecomprising part of the withdrawal unit and a blood collection chambercomprising part of the analyzer, the blood collecting chamber beingphysically separated from the cffluent tube and into which blood fromthe effluent tube is discharged.

12. In a blood monitoring system:

a catheter to be introduced into a patient by a needle;

a blood withdrawal/intravenous infusion apparatus having means operatingin a withdrawal mode and means operating in an infusion mode comprising:

blood withdrawal passageway means in fluid communication with thecatheter, at least one blood monitoring site along the passageway meanscomprising means for evaluating blood, power means for withdrawing bloodthrough the catheter and passageway means to the monitoring site whenthe withdrawal operating means are caused to function,

control means for shifting the unit between said two modes;

infusion means comprising a source of infusion fluid a first flow pathcomprising part of said passageway means including the blood monitoringsite spanning between the source of infusion fluid and the catheter, asecond flow path spanning between the source and a waste station, andpressure-creating means to drive the fluid along (a) the first flow pathwhen the control means have set the infusion operating means to functionand (b) the second flow path when the control means have set thewithdrawal operating means to function.

mg? UNITED STATES PATENT VGFFICEY CERTIFICATE OF CORRECTION Patent I2338-682 Dated October 1. 107 4 lnventofls) ustin Clark et al.

It is certified that errorvap'pears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 6; line t, "to the collector 32" should read --to the connector32--.

Column 7, line 7, "the source 1H0 should read ---the pump l lO;--.

Column 9 line 3, "with regard" should read --without regard--.

Column 9, line 40, "electric singals" should read eIectric signals-.

Column 10, line 13, after "calibration" insert --of the unit. That is,in the process of using calibration--.

Column '12, lines 19-20, "130 the patieint" should read --l30 to thepatient--.

Column 12, line 31, "262a 262b" should read --262a and 262b--. o

Column 15, line :36, "following a 45 second" should read --following a10-5 second- Column 15, line 16, "tubing 232, the because" should read--tubing 232, and because- Column 15 line 59', "gas tester 3,2commences" should read --gas tester 23 commences--.

Column 16 line 61, "period of 15 seconds" should read --period of 10-5-secondsa Signed and sealed this" 11th day of March 197 (SEAL) Attest:

c. MARSHALL DANN RUTH C MASON I Commissioner of Patents I AttestlngOfficer and Trademarks

1. An automated blood unit comprising: first and second fluid valves,each having a normal position and an operated position; a first fluidpath means adapted to be connected to an indwelling blood catheter forinterconnecting said catheter with a first port of said first fluidvalve; a second fluid path means connected to said first fluid pathmeans and to a first port of said second fluid valve; a third fluid pathmeans interconnecting a second port of said second fluid valve with asecond port of said first fluid valve; a reversible pump; means forinterconnecting said pump with a third port of said first fluid valve;said first fluid valve comprising first fluid communicating means, whenin its normal position, connecting said first fluid path means with saidpump, and also comprising second fluid communicating means when in itsoperated position, connecting said third fluid path means with said pumpvia the interconnecting means, and said second fluid valve comprisingfirst fluid communicating means, when in its operated position,connecting said second fluid path means with said third fluid pathmeans, so that, with a catheter connected (a), in response to said pumpinitiating a draw cycle with said first fluid valve in its normalposition, fluid is drawn by force of said pump along a pathwaycomprising said first fluid path means, said first fluid communicatingmeans of the first fluid valve and said interconnecting means therebydrawing blood from said catheter into said first fluid path means, and(b) in response to said pump initiating a draw cycle with said first andsecond fluid Valves in their operated positions, fluid is drawn alonganother pathway comprising said second fluid path means, the first fluidcommunicating means of the second fluid valve and the third fluid pathmeans thereby drawing blood from said catheter into said second andthird fluid path means, and so that, in response to said pump initiatinga push cycle following said blood withdrawal into either of saidpathways, blood is returned to said catheter along said pathways.
 2. Theautomated blood unit according to claim 1 additionally comprising: anintravenous irrigation solution source connected to a third port of saidsecond valve, said third port being connected by second fluidcommunicating means to said second fluid path means when said secondvalve is in its normal position, a fourth port of said second fluidvalve and third fluid communicating means connecting said fourth port tosaid third fluid path means at the second port of the second valve whensaid second valve is in its normal position, said fourth port adapted todischarge to waste fluid passing from the third fluid path means andsaid third communicating means, said first fluid path being adapted tobe filled with saline solution, so that blood is withdrawn from saidcatheter into said first fluid path means due to negative salinepressure caused by the pump and thereafter returned to said catheterfrom said first fluid path means in response to positive fluid pressurecreated by the pump against the saline and thence against the blood whensaid fluid valves are in their normal positions, and blood is withdrawnfrom said catheter through the first fluid path means into said secondfluid path means due to negative saline pressure caused by the pump andthereafter returned to said catheter from said second fluid path meansalong said first fluid path means in response to positive fluid pressureof said intravenous solution when said pump is operated with said valvesin their operated positions.
 3. The automated blood unit according toclaim 1 wherein said first fluid path means includes an oximeterdisposed between the junction of said second fluid path means with saidfirst fluid path means and the point of connection of said catheter tosaid first fluid path means and wherein the oximeter comprises means fortaking oximeter readings by pump drawing a small sample of blood alongthe first fluid path means through the oximeter and then pump displacingat least a portion of the blood sample back along the first fluid pathmeans into the patient.
 4. The automated blood unit according to claim 1additionally comprising: a selectively disengagable connection means forconnecting said second fluid path means with said first fluid pathmeans, said connection means being adapted for connection to a secondindwelling catheter in lieu of the first fluid path means.
 5. Theautomated blood unit according to claim 1 additionally comprising: a lowpressure constant flow saline source connected by fourth fluid pathmeans to a fourth port of said first valve, said first valve comprisinga third fluid communicating means which, when the first valve is in itsnormal position, connects said saline source with said third fluid pathmeans, said first fluid valve also comprising fourth fluid communicatingmeans which, when said first valve is in its operated position, connectssaid saline source with said first fluid path means, the second fluidvalve comprising an additional port being connected by additional fluidcommunicating means to said third fluid path means, when said secondvalve is in its normal position, said fourth port adapted to dischargefluid passing therethrough to waste, so that said first fluid valve (a)connects said first fluid path means with said pump via said first fluidcommunicating means of the first valve and the interconnecting means andconnects said saline source with waste via said third fluidcommunicating means of the first fluid valve, the third fluid pathmeans, the additiOnal fluid communicating means and the additional portof the second fluid valve, when said first and second valves are intheir normal positions, and (b) connects said saline source to saidfirst fluid path means via said fourth fluid communicating means, to actas a blood clot preventing flush for a catheter connected to said firstfluid path means, when said first valve is in its operated position,said pump being simultaneously in communication with said secondcatheter via the interconnecting means, the second fluid communicatingmeans of the first valve, the third fluid path means, the first fluidcommunicating means of the second valve and the second fluid path means,said second valve being in its operated position.
 6. The automated bloodunit according to claim 5 including a blood pressure transducer in fluidcommunication with one of said pathways.
 7. A blood testing systemcomprising: a catheter to be introduced through the skin into thecardiovascular system of a patient using a sharp instrument; a bloodwithdrawal unit connected to the catheter, the blood withdrawal unitcomprising a closed fluid storage system comprising fluid pathway meanscomprising flexible tubing, the pathway having a uniform small borethroughout, which pathway means are initially filled with biologicallyinert fluid, blood flow means including two directional power meansimposing positive and negative pressures upon the inert fluid within thepathway means for withdrawing blood, under negative pressure, throughthe catheter into and expelling all of the withdrawn blood from thewithdrawal unit under positive pressure, said blood flow meanscomprising means for causing at least a substantial portion of thewithdrawn blood to be returned through the pathway means and thecatheter into the cardiovascular system under negative pressure causedby said power means, whereby upon withdrawal of blood through thecatheter into the uniform bore pathway means of the withdrawal unit saidblood flow means causes little if any turbulent flow resulting in anessentially two dimensional blood/fluid interface comprising anegligible amount of fluid with little or no mixing of blood and fluidand, thereafter, causing return of substantially all blood along thepathway means and into the cardiovascular system through the catheterand infusion into the cardiovascular system of very little inert fluidunder positive pressure caused by the power means.
 8. An automated bloodtesting system comprising: a catheter to be placed in the cardiovascularsystem of a patient through venipuncture; a blood withdrawal unitcomprising fluid passageway means in fluid communication with thecatheter, biologically inert fluid in said passageway means, at leastone test station disposed at a site intermediate the passageway means,and two way hydraulic pressure control means for removing bloodjuxtaposed the inert fluid through the catheter and along a pathcomprising said passageway means to said test station under hydraulicpressure at the same time withdrawing said inert fluid along the samepath thereby creating a movable interface between the blood and fluid;said withdrawal unit further comprising means at said test station sitefor testing said blood disposed in said passageway means at said stationand means creating hydraulic pressure which acts upon said inert fluidto jointly displace the inert fluid and blood in a reverse directionalong said path and thereby return essentially all of said removed bloodto the patient''s cardiovascular system through the catheter, said twoway control means having means terminating the return of blood to thecardiovascular system when the blood/fluid interface is juxtaposed thecatheter.
 9. An automated blood testing system comprising: a pluralityof sterile blood withdrawal units each withdrawal unit adapted to becoupled to a patient via a catheter placed through the skin into avessel by a sharp instrument and each withdrawal unit Defining anindependent blood flow path therethrough; a single non-sterile bloodanalysis unit comprising one-way blood ingress means which receivesblood from any selected one of said withdrawal units at any specifiedpoint in time, passageway means connected to the one-way blood ingressmeans, a plurality of blood testing sites disposed at various locationsalong the passageway means, each blood testing site comprising means forevaluating blood, means for displacing blood received at the one-wayblood ingress means along the passageway means to each testing site, andblood egress means for expelling blood from the analysis unit to waste;each withdrawal unit comprising means for removing blood from a patientthrough the associated catheter and flow path of the associatedwithdrawal unit to the one-way blood ingress means of the analysis unitand for returning blood to the patient which, following withdrawal, isdisposed within the flow path of said withdrawal unit between thecatheter and the one-way blood ingress means of the analysis unit. 10.An automated blood testing system comprising: a sterile blood withdrawalunit adapted to be coupled to a patient via a catheter placed throughthe skin into a vessel by a sharp instrument, the withdrawal unitdefining a blood flow path therethrough; a non-sterile blood analyzercomprising a one-way blood ingress interface in one-way communicationwith the blood flow path to receive blood from the withdrawal unit, theone-way blood ingress interface comprising means preventing blood flowfrom the analyzer back to the withdrawal unit, and passageway meansconnected to the one-way blood ingress interface, at least one bloodtesting site disposed at a location along the passageway means, theblood testing site comprising means for evaluating blood, means fordisplacing blood received from the withdrawal unit at the one-way bloodingress interface along the passageway means to the testing site, bloodegress means for expelling blood from the analyzer to waste; thewithdrawal unit comprising means for removing blood from the patientthrough the catheter and flow path of the withdrawal unit to the one-wayblood ingress interface of the analyzer and for returning to the patientresidual blood disposed within the flow path of the withdrawal unitbetween the catheter and the one-way blood ingress interface.
 11. Thesystem of claim 10 wherein the blood flow preventing means of theone-way blood ingress interface comprise a blood effluent tubecomprising part of the withdrawal unit and a blood collection chambercomprising part of the analyzer, the blood collecting chamber beingphysically separated from the effluent tube and into which blood fromthe effluent tube is discharged.
 12. In a blood monitoring system: acatheter to be introduced into a patient by a needle; a bloodwithdrawal/intravenous infusion apparatus having means operating in awithdrawal mode and means operating in an infusion mode comprising:blood withdrawal passageway means in fluid communication with thecatheter, at least one blood monitoring site along the passageway meanscomprising means for evaluating blood, power means for withdrawing bloodthrough the catheter and passageway means to the monitoring site whenthe withdrawal operating means are caused to function, control means forshifting the unit between said two modes; infusion means comprising asource of infusion fluid a first flow path comprising part of saidpassageway means including the blood monitoring site spanning betweenthe source of infusion fluid and the catheter, a second flow pathspanning between the source and a waste station, and pressure-creatingmeans to drive the fluid along (a) the first flow path when the controlmeans have set the infusion operating means to function and (b) thesecond flow path when the control means have set the withdrawaloperating means to function.